1. Field of the Invention
The present invention relates to a flexible tube for an endoscope which has a helical tube, and an endoscope having this flexible tube.
2. Description of the Related Art
When an inserting section of an endoscope is inserted into, for example, a lumen, the inserting section needs to smoothly bend from a distal end portion of the inserting section toward a proximal end portion of the inserting section to reduce a patient's pain and improve insertion-removal properties.
Such a structure is disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2010-104668, Jpn. Pat. Appln. KOKAI Publication No. 2012-120573 and Jpn. Pat. Appln. KOKAI Publication No. 2002-551.
For example, Jpn. Pat. Appln. KOKAI Publication No. 2010-104668 discloses an endoscope soft portion. This endoscope soft portion has a helical tube, a reticular tube that covers an outer peripheral surface of the helical tube, and an envelope layer that covers an outer peripheral surface of the reticular tube. In the helical tube, an initial tension is given from both sides in a longitudinal direction of the helical tube. An end portion of the reticular tube is fixed to an end portion of the helical tube, and elongation in the longitudinal direction of the helical tube is controlled.
For example, Jpn. Pat. Appln. KOKAI Publication No. 2012-120573 discloses a flexible tube. This flexible tube has a helical tube, a reticular tube that covers an outer peripheral surface of the helical tube, and an envelope that covers an outer peripheral surface of the reticular tube. The helical tube is a helical elastic tube member. The elastic tube member has a dense coil to which an initial tension is at least partially given.
For example, Jpn. Pat. Appln. KOKAI Publication No. 2002-551 discloses a flexible tube for an endoscope in which a bonding force among a helical tube, a braided body and an envelope is strong.